Field of the Invention
This invention relates to a hydrostatic axial piston machine with a housing; a drive shaft mounted so that it can rotate in the housing by a bearing device comprising at least one roller bearing; and a cylinder drum provided with at least one piston bore, with a longitudinally displaceable piston in each of the piston bores.
Description of Related Art
In hydrostatic axial piston machines, as a rule, the housing (inside of which the rotating drive shaft and the rotating cylinder drum are located) is filled with pressure medium, in particular hydraulic fluid, to provide cooling and lubrication. During operation of the axial piston machine, the rotating drive shaft and the rotating cylinder drum cause churning losses to occur, which increase extra-proportionally as the speed of rotation increases. These churning losses represent additional energy consumption which, in an axial piston machine in the form of a pump, represent an undesirable dissipation of energy which must be made up by the drive and in an axial piston machine in the form of a motor, are not available as output power. Especially at high speeds of rotation of the rotating components, this power loss can be on a significant order of magnitude, and as a result of which, the potential performance and utility of the axial piston machine can be restricted and limited at high speeds of rotation.
To overcome these disadvantages, it is known that the housing of a hydrostatic axial piston machine can be emptied of hydraulic fluid to reduce the losses caused by the churning of the rotating components and to increase the efficiency of the axial piston machine at high speeds of rotation.
However, in a hydrostatic axial piston machine in which the hydraulic fluid has been emptied from the housing, care must be taken to provide adequate lubrication and cooling of the roller bearings of the bearing device of the drive shaft. To guarantee adequate lubrication of the roller bearings of the drive shaft of the hydrostatic axial piston machine, DE 41 28 615 C1 and DE 198 29 060 B4 teach that a lubricant channel can be provided that carries the flow of lubricant and which is routed through all the roller bearings of the bearing device of the drive shaft.
To guarantee a uniform lubrication of the roller bearings with a lubricant channel of this type that is routed through the roller bearings, DE 198 29 060 B4 provides a back pressure device that dams up the lubricant in the lubricant passage at the roller bearing facing the cylinder drum. For this purpose, in DE 198 29 060 B4 the back pressure device is located downstream of the roller bearings of the bearing device in the lubricant channel. The roller bearing facing the cylinder drum and the axial edge located on the inner ring of this roller bearing with which the roller bodies of this roller bearing are in contact with their end surface is, thereby, lubricated and cooled with lubricant that has already been heated by the heat given off by the two roller bearings of the bearing device. As a result, adequate lubrication and cooling of the axial edge of the roller bearing facing the cylinder drum are not guaranteed.
Therefore, it is an object of this invention to provide an axial piston machine of the general type described above with a housing that has been emptied of hydraulic fluid but in which improved lubrication and cooling of the roller bearing are achieved in the vicinity of the axial edge of the inner ring of the roller bearing on the end surfaces of the roller bodies of the roller bearing.